title: Diagnostic usefulness of an amino acid tracer, α-[N-methyl-(11)C]-methylaminoisobutyric acid ( (11)C-MeAIB), in the PET diagnosis of chest malignancies.
abstract: OBJECTIVE
  Although positron emission tomography (PET) using [(18)F]-fluoro-2-deoxy-D-glucose ((18)F-FDG) is established as one of the first-choice imaging modalities in the diagnosis of chest malignancies, there are several problems to solve in clinical practice, such as false positive uptake in inflammatory diseases. The aim of this study was to evaluate the clinical usefulness of an amino acid tracer, α-[N-methyl-(11)C]-methylaminoisobutyric acid ((11)C-MeAIB), in the diagnosis of chest malignancies, in combination with (18)F-FDG.
  
  
  METHODS
  Fifty-nine cases (57 patients, 66 ± 12 years old) who consulted to our institution for the wish to receive differential diagnosis of chest diseases were included. Purpose of the studies were as follows: differential diagnosis of newly developed lung nodules, n = 22; newly developed mediastinal lesions, n = 20; and both, n = 17 (including lung cancer: n = 19, lymphoma: n = 1, other cancers: n = 2, sarcoidosis: n = 15, non-specific inflammation: n = 18, other inflammatory: n = 4, respectively). Whole-body static PET or PET/CT scan was performed 20 and 50 min after the IV injection of (11)C-MeAIB and (18)F-FDG, respectively.
  
  
  RESULTS
  (11)C-MeAIB uptake of malignant and benign lesions was statistically different both in pulmonary nodules (p < 0.005) and in mediastinal lesions (p < 0.0005). In visual differential diagnosis, (11)C-MeAIB showed higher results (specificity: 73 %, accuracy: 81 %), compared to those in (18)F-FDG (60, 73 %, respectively). In cases of sarcoidosis, (11)C-MeAIB showed higher specificity (80 %) with lower uptake (1.8 ± 0.7) in contrast to the lower specificity (60 %) with higher uptake of (18)F-FDG (7.3 ± 4.5).
  
  
  CONCLUSIONS
  (11)C-MeAIB PET/CT was useful in the differential diagnosis of pulmonary and mediastinal mass lesions found on CT. (11)C-MeAIB PET or PET/CT showed higher specificity than that of (18)F-FDG PET/CT in differentiating between benign and malignant disease. Our data suggest that the combination of (18)F-FDG and (11)C-MeAIB may improve the evaluation of chest lesions, when CT and (18)F-FDG PET/CT are equivocal.
authors.affiliation: Shiga Medical Center Research Institute, 5-4-30 Moriyama, Moriyama, Shiga, 524-8524, Japan.
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Nishii
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Higashi
authors.forename: Shinya
authors.initials: S
authors.lastname: Kagawa
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kishibe
authors.forename: Masaaki
authors.initials: M
authors.lastname: Takahashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamauchi
authors.forename: Hideki
authors.initials: H
authors.lastname: Motoyama
authors.forename: Kenzo
authors.initials: K
authors.lastname: Kawakami
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakaoku
authors.forename: Jun
authors.initials: J
authors.lastname: Nohara
authors.forename: Misato
authors.initials: M
authors.lastname: Okamura
authors.forename: Toshiki
authors.initials: T
authors.lastname: Watanabe
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakatani
authors.forename: Shigeki
authors.initials: S
authors.lastname: Nagamachi
authors.forename: Shozo
authors.initials: S
authors.lastname: Tamura
authors.forename: Keiichi
authors.initials: K
authors.lastname: Kawai
authors.forename: Masato
authors.initials: M
authors.lastname: Kobayashi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001692:Biological Transport; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D006801:Humans; D058610:Isobutyrates / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D013899:Thoracic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D014057:Tomography, X-Ray Computed; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D058610:Isobutyrates; D019788:Fluorodeoxyglucose F18; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; C020380:isobutyric acid